July 23 (Reuters) - Southern California Gas Co issued a natural gas curtailment watch on Monday, notifying customers to be prepared to reduce gas use if needed, with power generators expected to burn more fuel this week than usual to keep air conditioners humming as a heat wave blankets Southern California.

SoCalGas, a unit of California energy company Sempra Energy , said the watch would remain in effect until further notice.

High temperatures in Los Angeles were forecast to top 90 degrees Fahrenheit (32 Celsius) Monday-Friday with the mercury expected to reach 97 degrees (36 C)on Wednesday, according to AccuWeather. The normal high in the city at this time of year is 84 degrees Fahrenheit (29 C).

Gas supplies are expected to remain tight in Southern California this summer and winter due to reduced availability from SoCalGas' Aliso Canyon storage facility in Los Angeles, following a massive leak between October 2015-February 2016, and ongoing shutdowns of several pipelines.

SoCalGas projected gas demand would rise from 3.0 billion cubic feet per day (bcfd) on Monday to 3.1 bcfd on Tuesday and 3.2 bcfd on Wednesday, while receipts of the fuel via pipelines into California would only total about 2.6 bcfd each day.

That means SoCalGas will have to tap storage fields to make up the difference, which could hurt the utility's ability to stockpile enough fuel to avoid curtailments for some power and industrial customers on the coldest days during the winter heating season.

State and federal agencies have projected SoCalGas will only be able to deliver about 3.6 bcfd from non-Aliso storage fields due to the Aliso limitations and pipeline outages, which has only occurred once in the summer in the past five years but is fairly common in the winter.

State agencies forecast demand could peak at 4.9 bcfd on the coldest day in January.

To meet that peak, the agencies projected SoCalGas will be able to deliver between 2.7 bcfd and 3.3 bcfd via pipelines and 0.8-1.1 bcfd from non-Aliso storage facilities.

That would result in a shortfall of between 0.6 bcfd and 1.4 bcfd on that coldest day, which would require SoCalGas to use gas from Aliso to limit curtailments.

But since Aliso is only expected to be able to deliver less than 1 bcfd, SoCalGas would likely still have to curtail some deliveries to power plants on the coldest winter days, just like during a cold spell between Feb. 20-March 6 last winter.